Tainter gates are commonly employed in dams and canal locks, along the Mississippi River and elsewhere, to control water flow. Typically, tainter gates are floodgates having convex surfaces on the upstream sides of the gates, such that the flow of water toward and by the gates can assist in the opening and closing of the gates. A conventional tainter gate includes a pair of arms that are rotatably supported by way of shafts or “trunnion pins” that extend out of the tainter gate supports or “trunnion boxes” attached to the downstream sides of the dam piers on opposite sides of the tainter gate. The trunnion pins particularly pass through, and are supported on, two (or possibly more) anchor plates of the trunnion boxes.
Rotation of the tainter gate relative to the trunnion boxes (and thus relative to the river or other body of water and relative to the environment generally) particularly is accomplished at least in part by virtue of the rotation of trunnion pin bushings formed inside the casting of the arms through which pass the trunnion pins, relative to the trunnion pins themselves. That is, the trunnion pin bushings rotate relative to the trunnion pins when the tainter gate is raised or lowered. The overall combination of a tainter gate along with the associated trunnion boxes (including anchor plates) and trunnion pins and bushings, can be referred to as a tainter gate assembly or tainter gate structure.
Many tainter gate assemblies along the Mississippi River were installed in the 1930s and 1940s and, due to their age and correspondent wear and tear, are in need of repair. This is especially true of certain moving parts of the tainter gate assemblies. More particularly in this regard, the trunnion pins and/or trunnion pin bushings of many tainter gate assemblies are corroded such that the trunnion pin bushings cannot rotate freely relative to the trunnion pins. In such circumstances rotation of the tainter gate relative to the trunnion boxes will still occur, but largely (or entirely) only due to rotation of the trunnion pin bushings themselves relative to the orifices in the tainter gate arms in which the bushings are positioned. Over time, such rotation of the bushings within the tainter gate arms is undesirable, because it can damage the interfaces between the bushings and the tainter gate arms (and particularly the surfaces of the orifices of the arms in which the bushings are situated) as well as damage the interfaces between the bushings and trunnion pins. Damage to the interfaces particularly can occur due to misalignment of lubricant pathways formed along the junctions of the bushings and trunnion castings and/or a failure of lubricant to be provided along the junctions as a result of relative movement between the bushings and castings. Further, damage can occur even if the trunnion pins rotate relative to the anchor plates of the trunnion boxes, particularly if the trunnion pins are corroded.
Given these concerns, there is newfound interest in reconditioning many existing tainter gate assemblies, and particularly in replacing existing trunnion pins and trunnion pin bushings with new pins and bushings. Yet removal of trunnion pins from the trunnion boxes, particularly when the trunnion pins are corroded, has proven to be difficult. Replacement of the trunnion pins is complicated by the necessity of maintaining the integrity of the trunnion box and the anchor plates therewithin. In at least some circumstances, it is necessary that the trunnion pins be removed without employing extreme temperature changes that could affect the thermodynamic properties of the pin or anchor plate material (which could potentially damage the anchor plate material). Also, in at least some circumstances, it is necessary that trunnion pin removal be accomplished without the use of excessive jacking force, again to avoid damage to the anchor plates.
Recently, it has been determined that core drilling of the trunnion pins can be employed for the purpose of facilitating the removal of trunnion pins. Core drilling involves drilling out a core or central region of a trunnion pin along the entire length of the pin, while leaving an exterior sleeve portion of the original trunnion pin (or simply the “pin sleeve”) in place within the trunnion box (and anchor plates) for removal by way of a separate process. Use of core drilling in this manner is theoretically desirable because it does not require that any significant temperature changes be applied to the trunnion pin or trunnion box, nor does it require the application of any significant jacking force. Indeed, assuming pin sleeve removal is straightforward, the use of core drilling allows for careful removal of a trunnion pin in a manner that avoids damage to the trunnion box (and anchor plates thereof), and reduces the total cost of pin removal.
Yet core drilling in this manner is not fully satisfactory because removal of the pin sleeve in fact can itself be a difficult process. In particular, due to corrosion of the trunnion pin along its exterior surface that is in contact with the trunnion box (and anchor plates thereof) and trunnion bushing, removal of the pin sleeve typically cannot be accomplished simply by applying an axial force to the pin sleeve to draw it out of the trunnion box and trunnion bushing.
Further, supporting a core drill in relation to a trunnion pin to be drilled also is not straightforward. In particular, it is typically undesirable to mount core drill machinery upon a pier (or other structure) adjacent to the trunnion pin because typically there is too great of a distance between the mounting location and the drilling location to achieve satisfactory control over the drilling.
In addition to the above concerns, trunnion pin removal/replacement is also complicated because, when removing trunnion pins and bushings from tainter gate assemblies, it is necessarily the case that the tainter gates themselves be decoupled from the supports (their anchors) and must be supported in some other manner. However, the use of barges to perform support can be undesirable because, due to surging and/or changing water elevations, the elevation of the tainter gate will typically not remain steady. Further, supports positioned onto a river bottom can also be difficult to install because of diving equipment and unpredictable or undesirable surface conditions along the river bottom.
For at least these reasons, therefore, it would be advantageous if new or improved systems and/or methods can be developed for enabling the reconditioning of tainter gate assemblies and particularly for facilitating the removal and/or replacement of pin sleeves of trunnion pins following core drilling of those pins (and/or for supporting the core drilling machinery), and/or for supporting the tainter gates during such processes and/or at other times.